Mining machine with drive system for mining head gathering means,conveyor and traction means



Feb; 17,1970 w. amm cKm I ,.s,495;816*

MINING MACHINE WJETH 'DRIVE' SYSTEM FOR MINING HEAD GATHERING MEANS; CONVEYOR AND TRACTION MEANS 3 Sheets-Sheet. 1

Filed March 26, 1968 Feb. 17, 1970 w. M cRAcKEN 3,495,876 -MINING'MACHINE WITH'DRIVE SYSTEM FOR MINING HEAD GATHERING MEANS, CONVEYOR AND TRACTION MEANS Filed lla rch 26, 1968 3 Sheets-Sheet 2 7 bun Feb. 17,1970 w, MccR cKEN 3,495,876 MINING MACHINE W TH DRIVE SYS FOR MINING HEAD GATHERING MEANS, TRACTIO Filed March 26, 1968 r N MEANS TEM CONVEYOR AND I I 3 Sheets-Sheet 3' United States Patent 3,495,876 MINING MACHINE WITH DRIVE SYSTEM FOR MINING HEAD GATHERING MEANS, CON- VEYOR AND TRACTION MEANS William E. McCracken, Groveport, Ohio, assignor to Jeffrey Galion Manufacturing Company, a corporation of Ohio Filed Mar. 26, 1968, Ser. No. 716,104 Int. Cl. E21c 25/00 U.S. Cl. 299-64 24 Claims ABSTRACT OF THE DISCLOSURE A mining machine with a mining head, gathering means for the mined material, and a conveyor for the mined material. There is traction means to propel the mining machine to advance the mining head into the mine face, to move the gathering means into mined material to collect such material, and to generally propel the mining machine, as in moving from place to place in the mine. There are two motors which are connected by a mechanical drive system to the mining head, to the gathering means and to the conveyor to drive these elements. The two motors are also connected by a mechanical drive system to the traction means by which the traction means may be driven at either a high speed or an intermediate speed, and a third motor is provided for the traction means to drive the traction means at a low speed, all for the respective functions of the mining machine.

The instant invention relates to mining machines, and more particularly to an improved drive system for propelling the mining machine for advancing the mining head into the mine face, for collecting the mined material from the mine floor, and for moving from one mining place to another mining place.

Continuous mining machines are characterized by a mining head at the front end of the machine, gathering means to collect the mined material, also disposed at the front end of the mining machine, and conveying means to move the mined material to the rear of the mining machine to be discharged to a car or other conveyance for moving the material out of the mine. The mining head is adapted to be advanced into the mine face and is operated in and over the mine face to cut and break the material out of the mine face. The mined material falls to the mine floor and is collected by the gathering means and is swept into the conveyor of the machine. The conveyor extends longitudinally from the front end of the mining machine to the rear end of the machine and moves the material along the machine and discharges the material at the rear end of the machine.

The mining machine is equipped with suitable traction means, which may be endless crawler traction treads, by which the machine is propelled. Such traction means propels the mining machine forwardly to advance the mining head into the mine face, which is the sumping operation. The gathering means is operated during the cutting and breaking of the material from the mine face to collect the material as it is mined. However, the gathering means may also be operated in a clean-up operation, while the mining head is idle, to clean up any spillage of mined material that may be on the mine floor. During such clean-up the traction means are operated to propel the mining machine and the gathering means into the loose spilled material on the floor in order to gather it by the gathering means.

The continuous mining machine, which is constructed in accordance with this invention, has two motors which are disposed one at each side of the machine, and provide the power for operating the several mechanisms of the machine. The motors are continuously operated to provide a continuous source of power during the operation of the mining machine. There is a mechanical transmission driving means from the motors to the mining head by which the mining head is driven. Such transmission driving means includes clutches which are normally idle, and the clutches are engaged for connecting the driving means to the mining head to operate the latter. Similarly, there is a mechanical transmission driving means from the motors to the gathering means and to the conveyor for driving these mechanisms. The conveyor is driven at the same time as the gathering means, so that as the material is collected and is swept up by the gathering means it is being moved away by the conveyor, so that the machine does not get jammed with the mined material. A clutch is provided in the transmission driving means, and such clutch is normally idle and is engaged to connect the transmission driving means to the gathering means and to the conveyor to drive these elements. There is another normally idle clutch which is engaged to connect the transmission driving means to the gathering means and to the conveyor to drive the latter in the reverse direction, as in the case where a large piece may get caught or jammed and the mechanism is reversed to release the piece.

The traction means are also powered by the two motors of the mining machine. However, there is a third motor which also provides power for driving the traction means. The system is so constructed that the traction means may be driven at a high speed to propel the mining machine at a high speed, which is generally used in moving the mining machine from one mining place to another mining place in the mine. Such time that it takes to move the mining machine from place to place is non-mining or non-productive time, and therefore it is desired that such moves be accomplished as quickly as possible so as to consume a minimum amount of time. There is a high speed transmission drive for driving the traction means from one of the motors at a high speed that is used in moving the mining machine from place to place. There is a second transmission drive which operates at an intermediate speed to drive the traction means from the other motor at the intermediate speed that is less than the high speed. Such intermediate speed of the traction means is used to propel the machine in the mining place at the mine face, for example, as in moving the machine prior to advancing the mining head into the face, and in moving the mining machine for gathering the material from the mine floor. There is a normally idle clutch for the high speed transmission drive and a normally idle clutch for the intermediate speed transmission drive, and one clutch or the other clutch may be engaged to drive the traction means at the high speed or the intermediate speed, respectively.

In addition to the foregoing there is the third motor and a low speed transmission for driving the traction means at a low speed, that is used to advance the minning head into the mine face in the sumping out. The third motor is preferably a variable speed motor to provide a variable low speed operating range for driving the traction means. There is an overrunning clutch by which the third motor and the low speed transmission are connected to drive the traction means. Such clutch merely overruns when the traction means is driven by either the high speed transmission drive or by the intermediate speed transmission drive, and when neither of the latter is operated, the clutch engages when driven by the third motor and the low speed transmission. The traction means may be driven in forward or reverse directions, and for .this purpose there are normally idle forward and reverse clutches, which are engaged to drive the traction means either forward or reverse. Also, the forward or reverse clutch may be engaged in one side of the mining machine only, in which case only the traction means on the one side of the machine is driven and the machine may be steered in this manner. It is also possible to drive the traction means forward on the one side of the machine and to drive the traction means in reverse on the other side which also steers the machine.

It is an object of this invention to provide an improved drive system for a mining machine for controlling and operating the mining head, the gathering means, the conveyor and the traction means.

It is another object of this invention to provide an i proved drive system for a mining machine in which the traction means may be operated at different speeds for the functions of the mining head and the gathering means.

It is a further object of this invention to provide an improved drive system for a mining machine in which the traction means can be driven at a low speed for advancing the mining head into the mine face, at an intermediate speed for moving the machine for gathering mined material and for moving about in the mining place, and at a high speed for moving the machine to and from the mining place.

It is also an object of this invention to provide an improved drive system for a mining machine in which there are two continuously operating motors for the several operating elements of the mining machine, and one of the motors supplies power for operating the traction means at high speed, the other of the motors supplies power for operating the traction means at intermediate speed, and there is a third motor that supplies power for operating the traction means at low speed.

It is still another object of this invention to provide an improved drive system for a mining machine in which the propulsion means for the machine may be operated at high speed or intermediate speed by engagement of normally idle clutches, and the propulsion means may also be operated at a low speed by an over-running clutch that is engaged to provide the low speed operation.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

In the accompanying drawings:

FIGURE 1 is a side elevation view of a mining machine that incorporates the present invention;

FIGURE 2 is a top plan view of the mining machine shown in FIGURE 1;

FIGURE 3 is a perspective schematic view of the drive system to the traction means; and

FIGURE 4 is a perspective schematic view of the drive system to the mining head, to the gathering means and to the conveyor.

Referring to the drawings, in FIGURES 1 and 2, there is shown a mining machine with a mining head 11. The mining machine 10 is moved or propelled by endless traction treads 12, disposed one on each side of the machine. The endless traction treads 12, 12 are driven through a drive tranmission system by the electric motors 27R and 27L.

A gathering head 13 is pivotally mounted on the front of the mining machine 10. The gathering head 13 comprises an apron I14, the forward edge of which is disposed on the mine floor. There are gathering arms 15, 15 on each side of the apron '14 and these operate to gather th mined material from the mine floor on to the apron -14 and to sweep the mined material onto the chain and flight conveyor 16, which extends from the forward end of the mining machine 10 to the rear end thereof. The chain and flight conveyor 16 runs from the gathering head 13 to the conveyor discharge boom 17, which is also pivotally moun d on the mining mach n 10.

The gathering head 13 is pivotally mounted on the mining machine 10 by means of hydraulic cylinders 40, mounted on each side of the machine. Thus, the gathering head 13 may be adjusted upwardly and downardly to follow an uneven mine floor and thereby -to maintain the leading edge of the apron 14 on the mine floor for maximum effectiveness in loading the mined material onto the conveyor 16.

The discharge conveyor boom -17 is pivotally mounted on the mining machine 10 for movement upwardly and downwardly by means of hydraulic cylinders 41 so that the discharge of the mined material may be adjusted to meet the mine car hauling the material out of the mine. The tail portion of the discharge conveyor boom 17 may be swung from side to side by hydraulic cylinders 42, 42, as seen in FIGURE 2.

The mining machine 10 has a mining head 11 which is pivotally mounted on the mining machine 10 for movement upwardly and downwardly. The mining head 11 is supported on the mining machine 10 by a pair of arms 19, 19 which extend from the pivot 20 to the mining head 11. A reinforcing member 21 extends between the arms 19. There are two hydraulic cylinders 22, 22, which are connected to the arms 19, .19 to raise and to lower the arms 19, 1-9 and the mining head 11.

The mining head 11 includes a plurality of spirally arranged cutting bits 30 and a pair of cutting chains 31 which are also provided with a plurality of bits. The min ing head 11 is driven from the motors 27R and 27L through the drive transmission system 27R, 27L, shown in FIGURE 4. Shafts extending from the forward ends of the motors 27R, 27L drive gears 43R, 43L, respectively, which in turn drive bevel pinions 44R, 44L, through universal join-ts 45R, 46R, and 45L, 46L, respectively. Mining head clutches 47R, 471. are normally idle and when engaged, transmit the drive from bevel gears 48R, 48L to the gears 49R, 49L, respectively. The gears 49R, 49L drive the gears 50R, 50L through the intermediate gears 51R, 51L, respectively. The gears 50R, 50L are secured to the shaft 52, to rotate the latter and the mining head 11, which is also secured to the shaft 52.

The gathering arms 15, 15 on the gathering head 13 are also driven from the motors 27R and 27L. There are shafts 53R, 53L, which are driven from the rear of the motors 27R, 27L by suitable gearing. Shafts 3R, 53L drive gears 55R, 55L through universal joints 54R, 54L. Clutch 56R is normally idle and when it is engaged it transmits the drive from the gear 55R to bevel pinion 57R, which drives the bevel gear 58R to which there is secured the upright shaft 59R for a gathering arm 15. The bevel gear 60R is driven by the bevel gear 58R, and is secured to the cross-shaft 61 to drive the cross-shaft 61 and the bevel gear 60L, which is secured at the opposite end of the shaft 61. The bevel gear 60L drives the bevel gear 58L which drives the upright shaft 59L for the other gathering arm 15. The sprocket 62 is secured to the cross-shaft 61 and is driven by the latter to drive the chain and flight conveyor 16. The clutch 56R is engaged to drive the gathering arms 15, 15 and the conveyor 16 in the forward direction. There is another clutch 56L which is normally idle and it is engaged to drive the gathering arms 15, 15 and the conveyor in the reverse direction. The clutch 56L drives the gears SSL and the bevel pinion 57L, to drive the bevel gear SSL, and the latter drives the bevel gear 60L to drive the crossshaft 61 for the conveyor 16, and drives the upright shafts 59L, 59R for the gathering arms 15, 15.

The motors 27R, 27L are the power source for all the functions of the mining machine 10-. The motors 27R, 27L

drive the mining head 11 and drive the gathering arms 15, 15 and the conveyor 16. In addition the motors 27R, 27L drive the several hydraulic pumps (not shown) which operate the hydraulic equipment on the mining machine 10. The motors 27R, 27);. are operated continn ously during operation of the mining machine 10, and the operating elements of the mining machine are driven through the system of gears and clutches shown in FIGURES 3 and 4, which provides the operational control of the machine elements that is required in the mining operation. In FIGURE 3, there is shown the transmission drive system for transmitting power from the motors 27R, 27L to the traction treads 12R, 12L.

Referring to FIGURE 3, the motor 27R supplies power for driving the traction treads 12R, 12L of the mining machine 10 at high speed. The motor shaft 101, including the universal connection 102, is continuously rotated, and drives gears 104, 105 to drive shaft 106 and bevel gears 107, 109. The bevel gear 109 is connected to a normally idle clutch 108, and upon engagement of the latter the gear 109 is connected through the clutch 108 to drive the shaft 111 for high speed operation of the traction treads 12R, 12L.

The motor 27L supplies power for driving the traction treads 12R, 12L of the mining machine 10. The motor shaft 201, including the universal connection 202, is continuously rotated and drives gears 204, 205, to drive shaft 206, and bevel gears 207, 209. The bevel gear 209 is connected to a normally idle clutch 208, and upon engagement of the latter the gear 209 is connected through the clutch 208 to drive the shaft 211 for intermediate speed operation of the traction treads 12R, 12L.

In the high speed transmission drive, the shaft 111 drives gear 112 which drives gears 113, 122. The gear 113 is secured to shaft 115 which is connected to gear 116 through a normally idle forward clutch 114, and gear 122 is secured to shaft 121 which is connected to gear 120 through a normally idle reverse clutch 123. Gears 116 and 120 rotate in opposite directions and both engage the gear 117. Gear 117 is in driving engagement with the traction tread 12R through shaft 118, gears 119, 124, shaft 125, gears 126, 127, 128, shaft 129 and gears 130, 131. Either the forward clutch 114 or the reverse clutch 123 may be engaged to select the direction of rotation of the gear 117, and thus to drive traction tread 12R in forward or in reverse direction, respectively.

On the other side of the transmission drive system, the shaft 211 drives the gear 212 which drives gear 309 to drive gears 213, 222. Gear 213 is secured to shaft 215, which is connected to gear 216 through a normally idle reverse clutch 214. Gear 222 is secured to shaft 221, which is connected to gear 220 through a normally idle forward clutch 223. One or the other of the forward clutch 223 or the reverse clutch 214 may be engaged to determine the direction of rotation of the gear 217, which is driven by either gear 216 or gear 220. Gear 217 is in driving engagement with traction tread 12L through shaft 218, which drives gears 219, 224, to drive shaft 225, which drives gears 226, 227, 228, to drive shaft 229 and gears 230, 231.

There is a cross-shaft 300 with gears 301, 302 secured to the opposite ends of this shaft. The gear 301 engages gear 112 and the gear 302 engages gear 212. When the high speed clutch 108 is engaged to drive gear 112, the drive is transmitted across to the opposite side through gears 301, 302 on cross-shaft 300, to drive gears 212, 309, 213, 222. Similarly, when the intermediate speed clutch 208 is engaged to drive gear 212, the drive is transmitted across to the other side of the machine through gears 302, 301 on cross-shaft 300 to drive the gear 112 and the gears 113, 122.

There is a third motor 303, which may be a variable speed hydraulic motor, for driving the traction treads 12R and 12L at a low speed in a low speed range according to the speed of the third motor 303. The gears 304, 305, 306, 307 are driven by the motor 303. The gear 307 is connected to a gear 309 by an overrunning clutch 308. The gear 309 is in engagement with gear 212, and thus is driven by gear 212 when high speed clutch 108 or intermediate speed clutch 208 is engaged, during which the gear 309 overruns the gear 307. However, when high speed and intermediate clutches 108, 208 are idle, the gear 307 may be driven from motor 303 and it is then connected by overrunning clutch 308 to gear 309 to drive the latter, and in turn to drive gears 213, 222 on the one side of the machine, and gears 113, 122 on the other side of the machine, the latter being driven through gears 212, 302, cross-shaft 300 and gears 301, 112.

In the operation of the traction treads 12R, 12L the high speed clutch 108 or the intermediate speed clutch 208 is engaged for high speed operation or intermediate speed operation, respectively. The traction treads 12R, 12L are operated at a low speed in the low speed range of operation by maintaining the clutches 108, 208 disengaged and operating the variable speed hydraulic motor 303 at the selected speed. The drive is delivered from the motor 303 through the overrunning clutch 308. Then for forward propulsion of the traction treads 12R, 12L the forward clutches 114, 214 at the opposite sides of the machine are engaged, or for reverse propulsion the reverse clutches 123, 223 at the opposite sides of the machine are engaged. The forward and reverse clutches are selectively engaged to drive the final drive gears to the traction treads 12R, 12L. In order to steer the mining machine 10, the traction treads 12R, 12L may be driven on one side of the machine only, or the traction treads 12R, 12L may be driven in opposite directions at opposite sides of the machine.

Having thus described and shown an embodiment of the invention, what it is desired to secure by Letters Patent of the United States is:

1. A mining machine for cutting and breaking material from a mine face comprising a mining head that is adapted to be advanced into the mine face to cut and break the material from the mine face, traction means to propel the mining machine on the ground surface and to advance the mining head into the mine face, mining head driving means for operating said mining head to cut and break the material in the mine face, a first continuously operating motor and a second continuously operating motor to provide a continuous source of power, traction driving means for operating said traction means, first speed transmission means for operating said traction driving means at a first speed, first connecting means for said first motor and for said first speed transmission means and for said traction driving means to drive said traction means at a first speed, second speed transmission means for operating said traction driving means at a second speed, second connecting means for said second motor and for said second speed transmission means and for said traction driving means to drive said traction means at a second speed, and means to alternatively operate said first connecting means for connecting said first speed transmission means to said traction driving means in order to drive said traction means at said first speed or to operate said second connecting means for connecting said second speed transmission means to said traction driving means in order to drive said traction means at said second speed.

2. A mining machine a recited in claim 1, including a third motor for said traction means, and third connecting means for said third motor and said traction driving means in order to drive said traction means at a third speed.

3. A mining machine as recited in claim 1, including connecting means for at least one of said first and second motors and said mining head driving means for operating said mining head.

4. A mining machine as recited in claim 3, including gathering means for collecting mined material and a conveyor to move the mined material to the rear of the mining machine for discharge, driving means for said gathering means and said conveyor, and connecting means for at least one of said first and second motors and said gathering means and said conveyor for operating the gathering means and the conveyor.

5. A mining machine as recited in claim 4 in which said mining head connecting means includes a normally idle clutch that is engaged to make driving connection to the mining head, and said gathering means and conveyor connecting means includes a normally idle clutch that is engaged to make driving connection to the gather ing means and conveyor.

6. A mining machine as recited in claim 5, including another normally idle clutch that is engaged to make reverse driving connect-ion to said gathering means and conveyor to operate the latter in the reverse direction.

7. A mining machine as recited in claim 1, in which said first motor operates at a constant speed, said second motor operates at a constant speed, said first connecting means includes a first transmission means to drive said traction means at a first speed, a first clutch to connect said first transmission means to said traction driving means, said second connecting means includes a second transmission means to drive said traction means at a second speed, and a second clutch to connect said second transmission means to said traction driving means,

8. A mining machine as recited in claim 7, including a third motor for said traction driving means, third connecting means for said third motor and said traction driving means to drive said traction means at a third speed, said third connecting means including a third transmission means to drive said traction means at a third speed, and a third clutch to connect said third transmission means to said traction driving means.

9. A mining machine as recited in claim 8, in which said third motor is a variable speed hydraulic motor to operate the traction means in a third speed range accord ing to the speed of the hydraulic motor. I U

10. A mining machine as recited in claim 8, including a common driving element for said second transmission and for said third transmission, said third clutch including overrunning clutch means connected to said common driving element to drive the common driving element by either said second transmission or by said third transmission.

11. A mining machine as recited in claim 8, in which said traction driving means includes forward drive transmission means and reverse drive transmission means, means to selectively connected said forward drive transmission means or said reverse drive transmission means to operate said traction means in forward or reverse d1- rections, respectively.

12. A mining machine as recited in claim 1, lncludlng a high speed transmission gear drive connected to said first motor, a first clutch to engage said high speed transmission gear drive, an intermediate speed transmlssion gear drive connected to said second motor, a second clutch to engage said intermediate speed transmission gear drive, a forward gear drive for said traction means and a reverse gear drive for said traction means each of WhlCl'l 18 adapted to be driven by either said high speed transmission gear drive or said intermediate speed transmission gear drive, a forward clutch to engage said forward gear drive, a reverse clutch to engage said reverse gear drive, a final gear drive connected to said traction means and connected to said forward gear drive and to said reverse gear drive to be driven by either of said forward gear drive or said reverse gear drive.

13. A mining machine as recited in claim 12, including a low speed transmission gear drive, a third clutch to engage said low speed transmission gear drive, said third clutch being an overrunning clutch connected to a gear of said intermediate speed transmission gear drive and connecting said low speed gear drive to said forward gear drive and to said reverse gear drive.

14. A mining machine for cutting and breaking material from a mine face comprising, a mining head that is adapted to he advanced into the mine face to cut and break the material from the mine face, first traction means at one side of the mining machine and second traction means at the other side of the mining machine to propel the mining machine on the ground surface and to advance the mining head into the mine face, mining head driving means for operating said mining head to cut and break the material in the mine face, a first continuously operating motor at said one side of the mining machine and a second continuously operated motor at said other side of the mining machine to provide a continuous source of power, first traction driving means for operating said first traction means, second traction driving means for operating said second traction means, first drive transmission means connected to said first motor to drive said traction means at a first speed, first drive connecting means for said first drive transmission means to connect to said first traction driving means and to said second traction driving means, second drive transmission means connected to said second motor to drive said traction means at a second speed, second drive connecting means for said second drive transmission means to connect to said first traction driving means and to said second traction driving means, cross drive means to connect said first traction driving means and said second traction driving means from one side of the mining machine to the other side of the mining machine for mutual operation of both said first traction means and said second traction means alternatively from either of said first drive transmission means or from said second drive transmission means.

15. A mining machine as recited in claim 14, including a third motor to provide another source of power for said first traction means and for said second traction means, third drive transmission means connected to said third motor to drive said traction means at a third speed, third drive connecting means for said third drive transmission means including said cross drive means.

16. A mining machine as recited in claim 15, in which said first motor operates at a constant speed, said second motor operates at a constant speed, and said third motor is a variable speed hydraulic motor to operate the traction means in. a third speed range according to the speed of the hydraulic motor.

17. A mining machine as recited in claim 15, in which said third drive transmission means includes overrunning clutch means connected to said first drive connectmg means and to said second drive connecting means and to said cross drive means to overrun said third drive transmission means when said traction means is driven at said first speed or at said second speed. 18. A mining machine as recited in claim 17, including a common driving element for said third drive trans IIllSSIOIl means, for said first drive connecting means, for said second drive connecting means, and for said cross drive means, and said common driving element being connected to said overrunning clutch.

19. A mining machine as recited in claim 14, in which each of said first traction driving means and said second traction driving means includes forward drive transmission means and reverse drive transmission means, a final drive transmission means from said forward drive tranmission means and from said reverse drive transmission means to said first and second traction means, repectively, forward drive connecting means for said forward drive transmission means and said final drive transmission means and reverse drive connecting means for said reverse drive transmission means and said final transmission means to alternatively drive said traction means in forward or reverse directions.

20. A mining machine as recited in claim 14, in which said first drive connecting means comprises a first normally idle clutch, said second drive connecting means com-prises a second normally idle clutch, said first clutch and said second clutch being alternatively engaged to connect said first drive transmission or to connect said second drive transmission, respectively.

21. A mining machine as recited in claim 19, in which said forward drive connecting means includes a normally idle forward clutch, said reverse drive connecting means includes a normally idle reverse clutch, said forward clutch or said reverse clutch being alternatively engaged to drive said traction means in forward or reverse directions.

22. A mining machine as recited in claim 15, in which said first drive transmission means comprises a high speed gear train, said second drive transmission comprises an intermediate speed gear train, and said third drive transmission means comprises a low speed gear train.

23. A mining machine as recited in claim 22, said first drive connecting means comprises a normally idle first clutch and first gears driven from said high speed gear train upon engagement of the first clutch, said second drive connecting means comprises a normally idle second clutch and second gears driven from said intermediate speed gear train upon engagement of the second clutch, and said third drive connecting means comprises an overrunning clutch connected from said low speed gear train to drive said first gears and said second gears.

24. A mining machine as recited in claim 23, in which each of said first traction driving means and said second traction driving means includes forward drive gears and reverse drive gears connected to be driven alternatively from said first gears or said second gears, a final drive gear train from said forward drive gears and from said reverse drive gears to said first and second traction means, a normally idle forward clutch to connect said forward drive means to said final drive gear train upon engagement of the forward clutch, and a normally idle reverse clutch to connect said reverse drive means to said final drive gear train upon engagement of said reverse clutch.

References Cited UNITED STATES PATENTS 1,836,277 12/1931 Osgood 299 2,548,952 4/1951 Crossland 29959 X 2,733,057 1/1956 Letts 29959 X ERNEST R. PURSER, Primary Examiner US. Cl. X.R. 173-24; 29976 

